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Author: search.filters.author.Pulphol, PhierayaSubject: search.filters.subject.Dielectric

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    EFFECT OF FIRING TEMPERATURE ON THE PHASE FORMATION, MICROSTRUCTURE, AND ELECTRICAL PROPERTIES OF BST-BZN CERAMICS
    (2025-01-01)
    Somsri, Widchaya
    ;
    Duangkeaw, Panadda
    ;
    Sumang, Rattiphorn
    ;
    Pulphol, Phieraya
    ;
    Vittayakorn, Naratip
    Lead-free 0.88Ba0.8Sr0.2TiO3-0.12Bi(Zn2/3Nb1/3)O3 (BST-BZN) ceramics were prepared by the solid-state combustion technique, using glycine as fuel. The BST-BZN ceramics were calcined between 900–1100°C for 2 h and sintered between 1300–1400°C for 2 h. A pure perovskite phase with a pseudo-cubic structure was observed by XRD and confirmed by the Rietveld refinement technique. The average particle and grain sizes tended to increase with increased calcination and sintering temperatures. The measured density was in the range of 5.65–5.90 g/cm<sup>3</sup>. The dielectric constant (εr) and dielectric loss (tan δr) decreased with increased sintering temperatures, up to 1350°C and then increased. The energy storage density (Wtotal) and energy storage efficiency (η) of the ceramics were 0.488 J/cm<sup>3</sup> and 94.1% measured at 100 kV/cm, respectively, obtained by the sample sintered at 1375°C
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    Interlayer alkali ion governs robustness, reactivity, and dielectric properties of sintered lepidocrocite titanate
    (2022-01-01)
    Maluangnont, Tosapol
    ;
    Pulphol, Phieraya
    ;
    Vittayakorn, Wanwilai
    We investigate the structure across different length scales including the dielectric properties of Cs<inf>0.7</inf>Zn<inf>0.35</inf>Ti<inf>1.65</inf>O<inf>4</inf>, Rb<inf>0.75</inf>Zn<inf>0.375</inf>Ti<inf>1.625</inf>O<inf>4</inf>, and K<inf>0.8</inf>Zn<inf>0.4</inf>Ti<inf>1.6</inf>O<inf>4</inf> sintered at T<inf>S</inf> ​= ​900–1100 ​°C, where the lepidocrocite-type crystal structure is preserved. The increasing interlayer distance in the Rb-/K-analog is explained by the alkali loss which reduces the electrostatic attraction between the sheets and the interlayer ion. Meanwhile, the interlayer contraction in the Cs-analog is rather unusual. The increasing (decreasing) interlayer distances correlate to upshift (downshift) of the Ti-O vibration in the Raman spectra. The three compositions show varied grain orientation depending on the interlayer ion and T<inf>S</inf>. The dielectric permittivity differs by one order of magnitude in the order Cs<inf>0.7</inf>Zn<inf>0.35</inf>Ti<inf>1.65</inf>O<inf>4</inf> « Rb<inf>0.75</inf>Zn<inf>0.375</inf>Ti<inf>1.625</inf>O<inf>4</inf> « K<inf>0.8</inf>Zn<inf>0.4</inf>Ti<inf>1.6</inf>O<inf>4</inf>, suggesting the interlayer ion as the dominating dipole. The influences of T<inf>S</inf>, pellet density (i.e., alkali loss), and grain size/morphology/orientation on the dielectric permittivity are discussed. The understanding of the response to a high temperature treatment would be beneficial not only to specimen fabrications for physical properties measurements, but also to applications where the thermal stability is of concern.